<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .textColor{
      color: red;
    }
    span{
      color: blue;
    }
    div span{
      color: green;
    }
  </style>
</head>
<body>
  <p>段落1</p>
  <p class="textColor">段落2</p>
  <p>段落3</p>

  <button class="textColor">我是按钮</button>

  <span>外面得span</span>
  <div><p><span>div里面的span</span></p></div>

</body>
</html>